Which thermostat for updated water pump?

[JamesLond]

I've got a 2001 yukon and I got the water pump with the p/n 12703898 that has the number 12681178 stamped on it.

I'm really confused about what thermostat to use. The description at ac delco for the water pump says:

Years: 2001-2001
WHEN USING IN 2000 APPLICATIONS,USE 2004 THERMOSTAT FOR SERVICE

Which is weird since there's like 3 different years being mentioned.

The one I have now has the p/n 15-10412 and the one I ordered has the p/n 15-11057. I'm trying to get it right since I read some stories of snapped bolts.

 

[SnowDrifter]

I believe you are correct in ordering p/n XX057

The '04+ thermostat was updated to include a larger valve

See here:
Updated on top, original on bottom



Note that you absolutely should not be snapping bolts here. The t-stat housing will sit flush (or nearly) with the water pump before tightening bolts. There might be 2-3mm gap because of spring tension / gasket. But if you push it flush by hand, it shouldn't take more than 4-5 pounds of force. If it doesn't fit, then don't force it.

The housing doesn't need to be tight. Like, at all. It's only 11ftlbs. Torque wrench is great if you have it. Otherwise, you can 'calibrate yourself.' A jug of milk weighs about 8lbs. Lift that with your pointer finger. Feel how much force that takes? Ok now put your ratchet on, and with one finger, approximate that much force on the very end of the handle.